Egon Klamt

The effect of 10% HF treatment on the resolution of CPMAS 13C NMR spectra and on the quality of organic matter in Ferralsols

The investigation of the chemical composition of soil organic matter (SOM) in Ferralsols by means of solid-state cross-polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy is limited by their high iron oxide concentration and their low organic carbon content. In order to circumvent those limitations, such samples are often treated with hydrofluoric acid (HF) to remove paramagnetic material and to concentrate the amount of SOM. The main objectives of this study were to elucidate the impact of this approach on the resolution of the CPMAS 13C NMR spectra and on the chemical composition of the SOM in the A and B horizons of four Brazilian Ferralsols. Therefore, those soils were subjected to up to eight successive treatments with 10% (w/w) HF. Each of those extractions resulted in an enhancement of the C content of the samples. A relationship between mass loss caused by the treatment and texture and mineralogy was observed. However, high losses of carbon occurred during the HF treatments, particularly in the B horizons, but no consistent alterations in the distribution of carbon functional groups were determined by CPMAS 13C NMR, suggesting that preferential loss of specific carbon groups was not induced. The concentration of total and dithionite extractable Fe increased after two treatments for most of the samples. This may be best explained by the preferential dissolution of silicate leading to a selective enrichment of iron containing minerals. After four treatments, the Fe concentration declined considerably. After the second treatment, the spectral resolution improved. Considering the obtained results, it can be confirmed that the efficiency of the HF treatment is rather controlled by the number than by the duration of the extraction. We suggest that, for A horizons of Ferralsols, four repetitions of HF treatment are sufficient to yield well-defined spectra. For their B horizons, on the other hand, the CPMAS 13C NMR spectra obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

Pedotransfer functions for the estimation of moisture retention characteristics of Ferralsols and related soils

Abstract The determination of water retention characteristics of soils in tropical regions is hampered by the lack of adequate laboratory equipment and high cost of analysis. In this paper the possibilities of estimating water retention characteristics from routinely determined properties of Ferralsols/Oxisols and related soils are investigated. Two sets of data on soils from South America, Africa and South East Asia, were analyzed. Set 1 (91 samples from 31 profiles) was used for multiple linear regression to correlate water retention and parameters of the ‘Van Genuchten equation’ (a semi-empirical expression for the water retention curve) to other soil properties. Set 2 (35 samples from 13 profiles) was used as an independent data set to test the results obtained for Set 1. In Set 1, clay and silt accounted for 84% of the variance in moisture content at 10 kPa (θ10 kPa) and for 80% at 1.5 MPa (θ1.5 MPa). Adding organic carbon to the regression equation for θ10 kPa increased the explained variance to 86%, whereas expressing clay and silt contents on a volume basis instead of a mass basis increased the explained θ1.5 MPa variance to 83%. The avialable water storage capacity (AWC, here defined as moisture retained between 10 kPa and 1.5 MPa, θ10 kPa−1.5 MPa) showed significant correlations (at 1% level) with clay content, bulk density, and specific surface area, but not more than 48% of its variance could be explained. Parameters of the Van Genuchten equation showed significant (at 1% level) correlation with particle-size fractions, dithionite-extractable Fe and Al, organic-C content, and cation exchange capacity. Application of the estimated Van Genuchten equation to Set 1 resulted in a variance reduction of 79% for θ10 kPa, 75% for θ1.5 Mpa, and 45% for θ10 MPa. The results for Set 2 suggest that predicting AWC is most accurate when equations are used that are based on direct correlation between θ10 kPa−1.5 MPa and easily measured soil properties. Predictions based on th Van Genuchten equation, or on subtracting an equation for θ1.5 MPa from another one for θ10 kPa were inferior: they had even larger mean errors than predicting θ10 kPa−1.5 MPa as just the average value of Set 1.

Large area spatial variability of soil chemical properties in central Brazil

Abstract Understanding the spatial distribution pattern of soil properties is important to determine soil constraints to plant nutrition and appropriate management of soil resources in recently cultivated areas. This study addresses spatial variability of exchangeable potassium (Ke) and sum of bases (SB) in Mato Grosso State, Brazil. Geostatistical methods described the spatial variability and predicted along four transects crossing different soil mapping units and land use types. Ordinary kriging appropriately estimates values in unsampled areas. It identifies places where more intensive sampling is required. This study shows that land use affected spatial variability of Ke and SB in well-defined structural patterns. In particular, Ke exhibits a strong spatial dependence and anisotropy in two horizons. Traditional surveys of soil fertility, together with data from soil survey maps, can be used in combination with geostatistics by decision-makers to support management planning and to predict indicators related to soil quality as a measure of sustainability. As it turns out, Ke and SB need to be sampled at different densities, and soil survey information can be used to advantage to reduce the sampling efforts of SB by 96%.

Relação entre os constituintes do solo e seu comportamento espectral

The spectral soil reflectance is an expression that characterizes the electromagnetic radiation reflected by soil surface. Most of the soil constituents can be identified and sometimes quantified by the spectral behavior. The main soil constituents that influence its spectral behavior are the organic matter, iron oxides, mineralogy and clay content and moisture. The use of soil reflectance allows to obtain information to quickly identify and quantify the soil characteristics, both in laboratory and orbital levels, but it has been tested and used mainly in developed countries. In Brazil, the research interest for the study of the soil spectral reflectance started in the 1980’s, being a recent research area which needs research support to achieve a better understanding of the spectral interaction among the different components of the soil.

Tempo de uso agrícola e propriedades químicas de dois Latossolos do Planalto Médio do Rio Grande do Sul

From 1920 on, Ferralsols of the Planalto Medio region in the State of Rio Grande do Sul, Brazil, originally under forest vegetation, were converted into agricultural land, while the same soils under grassland were converted in the 1960-ies. Thereafter, chemical soil properties were affected by intense cropping, mainly of soybean and corn. To evaluate how the time of agricultural land use affected two Ferralsols in the Fortaleza dos Valos county, State of Rio Grande do Sul, pedon samples of a clay textured dystrophic Red Latosol and a medium textured dystrophic Red Latosol were collected under forest and grassland vegetation, respectively, on the top of the landscape and from soils under agricultural cultivation for eight to over 33 years. Concentrations of clay and organic matter; available and total P and K; exchangeable Ca, Mg and Al; and pH were determined. Base (V%) and aluminium (m%) saturation were calculated. Where the soil had been forested the organic matter content decreased after longer periods of agricultural use. On the other hand, the organic matter content increased as the time of agricultural use increased where the soil vegetation had been native grass. Ca + Mg contents increased while Al content and saturation decreased with the time of agricultural use. Originally Al-saturated soils under native vegetation gradually turned into soils with less than 50% of base saturation through the agricultural use. The total soil P increased notably in the surface horizons, while the total soil K also increased in deeper layers.

Variabilidade espacial de micronutrientes em solo sob pivô central no sul do Estado de Mato Grosso

RESUMO - Este estudo foi desenvolvido para identificar, caracterizar e comparar a estrutura dadependencia espacial dos micronutrientes boro, cobre, ferro, manganes e zinco soluveis em um LatossoloVermelho-Escuro sob pivo central apos 14 anos de uso intensivo, no sul do Estado de Mato Grosso. Oesquema de amostragem consistiu de coletas de 132 amostras com espacamento regular de 167 m,especialmente idealizado para determinar a variabilidade espacial em distância de ate 1 m. Com excecaodo zinco, o uso intensivo propiciou um aumento significativo nas concentracoes desses nutrientes nacamada mais afetada pelo manejo (0-20 cm), mesmo assim insuficientes para atingir o nivel criticoestabelecido para a regiao. Cerca de 95% das amostras de boro, 75% das amostras de cobre, 95% dasamostras de manganes e 1,5% das amostras de zinco apresentaram valores abaixo do nivel critico,distribuidos diferentemente pelos quadrantes, o que mostra que as praticas de fertilizacao e/ou asoperacoes de preparo de solo nao foram eficientes na distribuicao e homogeneizacao dos fertilizantes.Termos para indexacao: geoestatistica, agricultura de precisao.SPATIAL VARIABILITY OF MICROELEMENTS IN SOIL UNDER CENTER PIVOT IRRIGATIONSYSTEM IN SOUTHERN MATO GROSSO STATE, BRAZILABSTRACT - This study was carried out to identify, characterize and compare spatial structures ofboron, copper, iron, manganese and zinc in a Dark-Red Latosol under crop field intensively managedfor 14 years with a center pivot irrigation system in the Southern Mato Grosso State, Brazil. The soilsampling scheme, consisting of 132 systematic sampling, in which sampling points were located atregular intervals of 167 m, in such a way that it was possible to determine the soil variability at 1 mdistance. The result showed that, with exception of the zinc, the intensive land use increased significantlythe nutrients concentration in the upper layer, however it was insufficient to reach the critical levelestablished for the region. About 95% of boron samples, 75% of copper samples, 95% of manganesesamples and 1.5% of zinc samples presented values below the critical level. These values weredifferently distributed by the quadrants in the center pivot, showed that fertilizers application and /or soiltillage were not efficient to distribute and to homogenize the fertilizers.Index terms: geostatistics, precision agriculture.

Evaluation of morphological, physical and chemical characteristics of Ferralsols and related soils

Morphological, physical and chemical data of 58 soil profiles of Ferralsols and low activity clay Cambisols, Lixisols, Acrisols and Nitisols and of Alisols of the International Soil Reference and Information Centre (ISRIC) collection, described and sampled in eighteen different countries of tropical and subtropical regions, were selected to analyse their consistency and, or, variability and to search for properties to better describe and differentiate them. The soil profile descriptions were based on the guidelines of FAO and the FAO endorsed analytical methods of ISRIC. Frequence diagrams of the data show an asymmetric positively skewed and leptokurtic distribution for sand and silt fractions, specific surface, exchangeable bases and cation exchange capacity. Clustering soil colour hues, values and chromas rendered four distinct clusters, respectively of Rhodic, Rhodic/Xanthic (Haplic), Xanthic and Humic properties. The same technique applied to particle size distribution also originated four clusters, respectively of fine loamy, fine silty, clayey and fine clayey soils. Most of the soils analysed are acid, with low base saturation, except for Rhodic Nitisols and Rhodic Ferralsols, which present low exchangeable aluminium. Higher and variable values of this property are found in the other soil classes studied. Cation exchange capacity is also low and related to the kaolinitic and oxihydroxydic composition of the clay material. Regression analysis applied to cation exchange capacity resulted in low correlations with clay and silt content and higher with organic carbon and specific surface and clay content.

Basalto moído como fonte de nutrientes

Basalt rocks are one of the most common parent materials of large areas of soil in southern Brazil. Several major plant nutrients are present in its composition. The objective of this study was to evaluate the effect of the addition of increased rates of ground basalt rock on the nutrient availability of soil, during three periods of incubation. The rocks tested were a microcrystalline and an olivine-basalt. The rates of basalt rock, corresponding to 0, 5, 10, 25, 50 e 100 t ha-1, basalt were incubated in a Dark Red Latosol and a Red Yellow Podzolic soil. The experiment was carried out under greenhouse conditions at the Agronomy School of Federal University of Rio Grande do Sul. After 30, 150 and 300 days of incubation, the contents of K, Ca, Mg, pH, H + Al, P and CEC of the incubated soils were determined. The different rates tested caused an increase in these variables. However, the increases observed were small, except for P, the value of which may have been overestimated by the extractor used. The release of these elements to the soil varied with incubation period, but not with rock type, with the exception of the concentrations of Ca and P, which were higher for the olivine-basalt. The small release of nutrients from the rocks indicates that these materials cannot be used as the major source of plant nutrients.

Mineralogia da fração argila de solos vermelhos com horizontes superficiais brunados do planalto de lages (SC)

Soils with brown or yellowish brown hues are dominant in the high altitude areas of southern Brazil. This feature is a consequence of the cool weather and high humidity conditions, which contribute for the formation of goethite and complete soil xantization. However, in some sites, soils present brown and yellowish brown hues in surface and transitional horizons, yet preserving red colors in subsurface horizons what may represent a relic of a drier and hotter climate condition from the past. In this work, structural characteristics of the iron oxides goethite and hematite were determined in reddish and brown/yellowish brown horizons to help understand the genesis of these soil features. Two profiles of Red Nitosols (Dark Red Podzolic soils) with brown/yellowish brown surface horizon were described and sampled in the Planalto de Lages, Santa Catarina, Brazil. Morphological, physical and chemical methods were employed to characterize these profiles. X-ray diffraction analysis was used for the iron oxide identification from soil horizons, laterite crust, pedotubules, and gibbsite nodules. Structural parameters of goethite in the brown/yellowish brown horizons were different from those in the red subsurface horizons, mainly with respect to isomorphic replacement of iron by aluminum which was higher in the former; hematite showed similar characteristics in all horizons. These differences and similarities, respectively, suggest that hematite and possibly part of the goethite with less substitution of iron for aluminum substitution were preferentialy dissolved in the surface horizons. Thus, surface horizon xantization may be a result from residual accumulation of goethite population with high replacement of iron by aluminum, and from new goethite formed by iron reprecipitation in the present environmental conditions.

Adensamento subsuperficial em solos do semi-árido: processos geológicos e/ou pedogenéticos

In the Low Plateaus of Pernambuco State, soils with subsurface compaction are found, which causes limitations in their use and consequently decreases agricultural productivity. With the objective to identify the occurrence of geological (lithological discontinuity) and/or pedogenetical processes involved in the genesis of this compaction, three representative soil profiles were chosen, distributed in a topographical sequence, located in the low plateaus in the municipality of Petrolina in semiarid zone of the State of Pernambuco - Brazil. Determination of granulometric distribution, sand fraction morphoscopy, sedimentologic parameters, density, porosity, calculation of sand and silt fractions free from clay and the relationships between fine sand, average sand, very fine sand/total sand and fine clay/total clay were studied. The results indicate that the subsurface compaction has not resulted from geological processes or due to lithological discontinuity, since the parameters studied did not present variations in depth, which indicates the occurrence of these processes.